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Task 1
Discuss the benefits and pitfalls of computer-based models used
within an industrial environment to get mechanical properties of a
sample of the limitation value of the stress and strain.
Often materials are subject to forces (loads) when they are used. Mechanical
engineers calculate those forces and material scientists how materials deform
(elongate, compress, twist) or break as a function of applied load, time,
temperature, and other conditions.
Materials scientists learn about these mechanical properties by testing materials.
Results from the tests depend on the size and shape of material to be tested
(specimen), how it is held, and the way of performing the test. That is why we use
common procedures, or standards.
Concepts of Stress and Strain
Stress can be defined by ratio of the perpindicular force applied to a specimen
divided by its original cross sectional area, formally called engineering stress
To compare specimens of different sizes, the load is calculated per unit area, also
called normalization to the area. Force divided by area is called stress. In tension
and compression tests, the relevant area is that perpendicular to the force. In shear
or torsion tests, the area is perpendicular to the axis of rotation. The stress is
obtained by dividing the load (F) by the original area of the cross section of the
specimen (AO).
Stress—Strain Behavior
Hooke’s Law
for materials stressed in tension, at relatively low levels, stress and
strain are proportional through:
constant E is known as the modulus of elasticity, or Young’s modulus.
Measured in MPa and can range in values from ~4.5x104 40x107 MPa
Sress-strain curve
Material Modulus (N/m2
stress-strain curve
The stress-strain curve characterizes the behavior of the material tested. It is most
often plotted using engineering stress and strain measures, because the reference
length and cross-sectional area are easily measured. Stress-strain curves generated
from tensile test results help engineers gain insight into the constitutive
relationship between stress and strain for a particular material. The constitutive
relationship can be thought of as providing an answer to the following question:
Given a strain history for a specimen, what is the state of stress? As we shall see,
even for the simplest of materials, this relationship can be very complicated.
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In addition to providing quantitative information that is useful for the constitutive
relationship, the stress-strain curve can also be used to qualitatively describe and
classify the material. Typical regions that can be observed in a stress-strain curve
are:
1. Elastic region
2. Yielding
3. Strain Hardening
4. Necking and Failure
Design/Safety Factors
To take into account variability of properties, designers use, instead of an average
value of, say, the tensile strength, the probability that the yield strength is above
the minimum value tolerable. This leads to the use of a safety factor N > 1 (varies
from 1.2 to 4). Thus, a working value for the tensile strength would be sW = sTS / N.
Yield strength
The yield point, is defined in engineering and materials science as the stress at
which a material begins to plastically deform. Prior to the yield point the material
will deform elastically and will return to its original shape when the applied stress
is removed. Once the yield point is passed some fraction of the deformation will be
permanent and non-reversible. Knowledge of the yield point is vital when
designing a component since it generally represents an upper limit to the load that
can be applied. It is also important for the control of many materials production
techniques such as forging, rolling, or pressing.
Elastic Limit
- The lowest stress at which permanent deformation can be
measured. This requires a complex iteractive load-unload procedure and is
critically dependent on the accuracy of the equipment and the skill of the operator.
Proportional Limit
- The point at which the stress-strain curve becomes non linear. In most metallic materials
the elastic limit and proportional limit are
essentially the same.
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Offset Yield Point (proof stress)
- Due to the lack of a clear border between the
elastic and plastic regions in many materials, the yield point is often defined as the
stress at some arbitrary plastic strain (typically 0.2%). This is determined by the
intersection of a line offset from the linear region by the required strain. In some
materials there is essentially no linear region and so a certain value of plastic strain
is defined instead. Although somewhat arbitrary this method does allow for a
consistent comparison of materials and is the most common.
Yield point.
If the stress is too large, the strain deviates from being proportional to the stress.
The point at which this happens is the yield point because there the material yields,
deforming permanently (plastically).
Yield stress. Hooke's law is not valid beyond the yield point. The stress at the
yield point is called yield stress, and is an important measure of the mechanical
properties of materials. In practice, the yield stress is chosen as that causing a
permanent strain of 0.002, which called as proof stresss. The yield stress measures
the resistance to plastic deformation.
The yield strength is the stress required to produce a small-specified amount of
plastic deformation. The usual definition of this property is the offset yield
strength determined by the stress corresponding to the intersection of the stressstrain
curve and a line parallel to the elastic part of the curve offset by a specified
strain. In the United States the offset is usually specified as a strain of 0.2 or 0.1
percent (e = 0.002 or 0.001).
A good way of looking at offset yield strength is that after a specimen has been
loaded to its 0.2 percent offset yield strength and then unloaded it will be 0.2
percent longer than before the test. The offset yield strength is often referred to in
Great Britain as the proof stress, where offset values are either 0.1 or 0.5 percent.
The yield strength obtained by an offset method is commonly used for design and
specification purposes because it avoids the practical difficulties of measuring the
elastic limit or proportional limit.
Anelasticity
Here the behavior is elastic but not the stress-strain curve is not immediately
reversible. It takes a while for the strain to return to zero. The effect is normally
small for metals but can be significant for polymers.
Tensile strength.
When stress continues in the plastic regime, the stress-strain passes through a
maximum, called the tensile strength (sTS) , and then falls as the material starts to
develop a neck and it finally breaks at the fracture point.
True Stress at Maximum Load
The true stress at maximum load corresponds to the true tensile strength. For most
materials necking begins at maximum load at a value of strain where the true stress
equals the slope of the flow curve.
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True Fracture Stress
The true fracture stress is the load at fracture divided by the cross-sectional area at
fracture. This stress should be corrected for the, triaxial state of stress existing in
the tensile specimen at fracture. Since the data required for this correction are often
not available, true-fracture-stress values are frequently in error.
Design/Safety Factors
To take into account variability of properties, designers use, instead of an average
value of, say, the tensile strength, the probability that the yield strength is above
the minimum value tolerable. This leads to the use of a safety factor N > 1 (varies
from 1.2 to 4). Thus, a working value for the tensile strength would be sW = sTS / N.
Evaluate the capabilities and limitations of computer-based models,
also the processes and applications used in solving this target
Limitations of SOLIDWORKS Flow Simulation
It is important to know the limitations of SOLIDWORKS Flow Simulation before you start
the process of modeling your engineering problem. The limitations include the following
common flow situations that can't be studied in the present version of SOLIDWORKS Flow
Simulation: chemically reacting flows, fluid mixing flows, multi-phase flows and moving
model parts. However, it should be pointed out that motion of walls can be specified as
boundary conditions in SOLIDWORKS Flow Simulation.
Critically evaluate and provide supported recommendations for the
mentioned species of computer-based models to an industrial
environment that would improve efficiency and problem-solving
As part of system development, many industries, including the automobile industry, make
substantial use of modeling and simulation to help understand system performance.
Modeling and simulation (sometimes referred to here as simulation) are currently used for
a number of applications in the Department of Defense, notably for training users of new
systems and to help support arguments presented in the analysis of alternatives (formerly
cost and operational effectiveness analyses) to justify going ahead with system
development. Its success in similar applications in industry, and its cost, safety, and
environmental advantages over operational testing, have raised interest in the use of
modeling and simulation in operational testing and evaluation (where it enjoys the same
advantages). The use of simulation to augment operational test design and evaluation (and
other related purposes such as to provide insight into data collection) has been strongly
advocated by DoD officials. Although a number of workshops have been devoted to the use
of simulation for assisting in the operational test and evaluation of defense systems, the
precise extent to which simulation can be of assistance for various purposes, such as aiding
in operational test design, or supplementing information for operational test evaluation,
remains unclear. Great care is needed to ensure that the information provided by modeling
and simulation is useful since the uncritical use of modeling and simulation could result in
the advancement of ineffective or unreliable systems to full-rate production, or, conversely,
the delay or return to development of good systems.
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Analyse the role of finite element analysis in modelling products and
systems to calculating the mechanical properties.
 Support beam, truss, plate and shell (thin and thick, compatible and incompatible
formulations) and brick elements.
 Support nodal, point, line, surface and area loads.
 Support thermal loads.
 Support linear and nonlinear nodal, line and surface springs
 Support coupled springs (advanced)
 Support tension only/compression only members.
 Support moment releases, rigid elements and rigid diaphragms.
 Support element stiffness modifications
 Support forced displacements.
 Supports multi-DOF constraints such as inclined support.
 Support both English and Metric units.
Critically analyse the finite element product and systems models that
help to find and solve potential performance or structural issues for
the drilling tool
The most common advantages of conducting an FEA during product development are as
follows:
 Capacity to model complex systems
 Reduced development time
 Analysis of different design configurations
 Performance and cost optimization
 Reduced testing
 Safety improvement
 Faster achievement of the required quality
 Improvement of data available to engineers in decision making
 Better understanding of all components of a system, allowing for a more rational design
How FEA Can Help You?
FEA gives engineers a clearer picture of how a product will react to stresses and reduces the
need for extensive prototyping. Thanks to FEA, engineers can evaluate complex geometry,
multiple material types and capture local effects without the need to build a single
prototype.
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FEA is helpful in structural analysis for all specialists involved in product development:
 Stress and structural engineers
 Dynamics engineers
 Loads engineers
 Designers
FEA can assist all these specialists in developing parts and products. It helps them to make
decisions throughout all phases of product development and to answer the following
questions, among others:
Will it break?
Will it deform too much?
Will it hold together?
Will it buckle?
Can it be lighter?
Can it be stronger or more durable?
By using FEA at the very beginning of your development process, you will save time and
money since FEA will permit you to find the right solutions during the product design stage.
In modern industries, FEA is now a key activity in the development of performant products.
No one questions the usefulness and power of such a tool.
Reduce Prototyping
Prior to the intensive usage of FEA, the development of products in the mechanical
structural industry was based on prototyping.
Prototypes were built at different key stages of the development process, so the
construction of dozens of prototypes before the final product was not unusual. Today,
prototyping is still used but less intensively, since a prototype is usually only built at the end
of the development process, to validate the concept.
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Use FEA to Demonstrate Proof of Concept
FEA permits the engineers to explore new concepts and demonstrate to the customers that
they meet their requirements, but also demonstrate that a new design will work better that
the current. FEA is a powerful tool to demonstrate proof of concept to your customers
before they sign a contract with you.
Use FEA to Contribute to Sustainability
Nowadays, achieving more sustainable product designs is a top priority for companies
worldwide. Again, FEA can help in this objective:
FEA permits to test the products before they enter the prototyping stage
FEA permits to reduce the material consumption
FEA permits to ensure that a new design will not compromise the quality and the durability
of the final product
Use FEA at Every Stage of Development
To achieve their objectives, the various industries require that engineers design safe,
reliable, and optimized products that also meet aggressive cost reduction targets. This is
why the usage of FEA to analyze complex mechanical structures has increased dramatically
in recent years. Consequently, deploying the latest simulation tools effectively, accurately,
and efficiently has never been more critical.
FEA is useful at every stage of product design, to explore various concepts, validate
designs and find new development solutions:
Before, to define the product: FEA helps the engineer create a feasible design.
After the product is designed: FEA permits the validation of the defined design.
After the product is released: FEA can be used to investigate product failures.
Due to faster computers and more efficient algorithms implemented into the FEA solvers,
the simulation technologies have become more powerful in the recent years. The
consequence is that FEA can now be used in a wider range of applications.
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How FEA Leads to a More Cost-Effective R&D Process?
Nowadays, some organizations are still wondering why they should implement FEA in their
R&D process. The three main reasons why it is worth integrating FEA into the R&D process
are:
FEA permits to eliminate the bad designs at the beginning of the development process:
For a range of practical examples, review, provide supported and
justified recommendations for recognising and solving potential
structural or performance-based issues, using finite element product
and systems models.
Automotive
In the automotive industry, FEA software simulations are performed to assess the structural
safety of designed components, such as chassis, anchors, suspension, bodyworks, etc. One
of the most interesting applications is virtual crash tests, where a dynamical simulation is
performed to predict deformations and energy absorption against crash impact. Here is a
link to a project simulating a car suspension’s deformation and stress.
Industrial Equipment
For industrial equipment design and engineering, finite element analysis software
Civil Engineering and Structural Design
For civil engineering and structural design, FEA software has unleashed the power of fast
and accurate analysis, with the possibility of automatically applying code load combos and
checking compliance. Typical analysis scenarios include static loading, equivalent static
loading, dynamic performance in seismic scenarios, natural vibration modes, and
frequencies calculation. Here is an example project performing structural analysis on a steel
structure:
Amr gamal ahmed
Determine the faults in the application of simulation techniques then
extract relevant information from simulation and trace potential
faults in this application of simulation techniques.
1) Inadequate integration into CAD systems
If designers cannot run the simulations in the design tool, the workflow will be disrupted
and the application made more difficult.
2) Slow performance
If results take too long, designers are slowed down and can run fewer simulations.
3) Inaccuracies
If designers can't trust simulations to give them the right clues, the results are useless.
Because their decisions are then based on inaccurate findings.
4) Insufficient flexibility
When designers need to redefine the preparation parameters for each design iteration,
change, or alternative, they will use simulations less often to understand the impact of an
update.
5) Complicated application
Simulation tools that make it too complicated to set up analyses pose a hurdle to designers,
reducing the likelihood of their use.
6) Special knowledge as a prerequisite
Designers can benefit from the groundbreaking findings of a simulation, but if the tool can
only be used with the knowledge of a studied FEA analyst, it is not readily available.
Critically review results through a series of guided exercises and
recommendations and evaluate the appropriate application of
simulation techniques that can support decision making.
With the definition, purpose, and uses of models examined, it is then instructive to ask,
“What makes a good model?” or “How does one evaluate a model?” The literature offers
some answers to this question. Several baseline conditions are discussed in the literature,
which specify the basic requirements for the use of a model; these can be considered a
minimum threshold of characteristics. As stated by Weinstein et al., “models should be
used only after careful testing to ensure internal accuracy (internal validity), to ensure that
their inputs and outputs are consistent with available data (calibration), and to ensure that
their conclusions make sense (face validity).”27
Weinstein et al. offer a summary of the key components of model validation, as well as
evaluation: (1) transparency; (2) verification; (3) corroboration; (4) face validity; and (5)
accreditation.27 Much attention is placed on validity in this evaluation methodology. Strong
emphasis is placed on assessing face validity, and using multiple modeling efforts to
establish convergent validity. Regarding model validation, they also warn against important
elements such as (1) the nature of change in contexts that are not accounted for in models,
(2) the rapid pace of technological change, and (3) population and sub-population
characteristics that may be subject to change not included in the model. They caution
modelers to be aware of changing contexts and applicability of models to other populations,
not initially studied.
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Task2
During your work in a factory,there is a problem in the part which
take the lubricant and pass it through nozzle below you want make
simulation using CFD taking into considerations
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Demonstrate the importance of CFD simulations and complete this
simulation which applied to evaluate pressure and velocity
distributions in the engineering setting.
1- It’s cheap (ish)
As CFD involves only electricity and enginner brain matter, it is wildly cheaper than
conducting wind tunnel experiments, which requires making actual models of what is going
to be tested. As a result, many teams and automakers tend to begin their studies on
computed ambients in order to obtain a fairly consistent model to get to the wind tunnel.
This leads us to the second point…
2- It gives much more flexibility to engineers.
Just like making a prototype is costly, adjusting a real model is something much more
expensive to do rather than quickly changing your computer-generated model. Thus,
engineers stand a much better chance to end up with a more refined end product, that will
spare that lovely petrol you worked so hard to buy or to shred tenths of seconds on the
race track
3- The final analysis can be much deeper than with experimental testing.
With CFD, you can analyse the force acting on the tiniest bit of your car, visualise all of the
streamlines alongside with the respective airspeed on each point and also the whole
pressure field around your object of study. Even on the best-instrumented wind tunnel in
the world, you cannot get such data with such ease. Again, this will result in a finer project
and a better product/track weapon.
4 The precision can be absurd
With numerical techniques being refined over the years, CFD has become a solid tool for
projecting anything where aerodynamics and other fluids (liquids and gases) play a big role.
Most of the time, wind tunnel testing is conducted in order to validate (i.e. to prove the
CFD model is indeed correct) the results obtained with computer simulations.
5 It is not only useful for aerodynamics, but for other parts of the car too!
Most internal combustion engines from the last 10 to 15 years have been made with help
of CFD. Basically anywhere you’ll see any type of fluid (gas or liquid) moving, I can assure
you someone has used CFD to do it. Some other examples? Intercoolers, air-conditioning,
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brake cooling and the list goes on. Computer simulation is here to stay, and the results are
everywhere.
Evaluate the application and limitations of CFD in an engineering
context then provide supported and appropriate recommendations
for improving efficiency and the generation of suitable meshes for
CFD simulations
.PHYSICAL MODELS
- CFD relies upon physical models of real world processes
- CFD solutions can only be as accurate as the physical models
NUMERICAL ERRORS
- Solving equations on a machine also introduces numerical errors, e.g
- Round-off error (due to finite word size available on computer, round-off errors will
always exist).
- Truncation error (due to approximations in the numerical models)
- Similar to physical models.
- The accuracy of the CFD solution is only as good as the initial boundary conditions
provided to the numerical model.
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Discuss and evaluate the modelling method and data accuracy
Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical
analysis and data structures to analyze and solve problems that involve fluid flows.
Computers are used to perform the calculations required to simulate the free-stream flow
of the fluid, and the interaction of the fluid (liquids and gases) with surfaces defined by
boundary conditions. With high-speed supercomputers, better solutions can be achieved,
and are often required to solve the largest and most complex problems. Ongoing research
yields software that improves the accuracy and speed of complex simulation scenarios such
as transonic or turbulent flows. Initial validation of such software is typically performed
using experimental apparatus such as wind tunnels. In addition, previously performed
analytical or empirical analysis of a particular problem can be used for comparison. A final
validation is often performed using full-scale testing, such as flight tests.
CFD is applied to a wide range of research and engineering problems in many fields of study
and industries, including aerodynamics and aerospace analysis, hypersonics, weather
simulation, natural science and environmental engineering, industrial system design and
analysis, biological engineering, fluid flows and heat transfer, engine and combustion
analysis, and visual effects for film and games.